Getting global axis value of the vertex with the lowest value
I'm a noob when it comes to python but won't this do the job?

import bpy
import bmesh 

object = bpy.data.scenes[0].objects["Cube"].data
vcount = len(object.vertices)
cube = bmesh.from_edit_mesh(object)

if (vcount &gt; 0):
    lowest = cube.verts[0]
    for i in range(vcount):
        if (lowest.co.z &gt; cube.verts[i].co.z):
            lowest = cube.verts[i]

    for v in cube.verts:
        if (v.co.z == lowest.co.z):
            v.select = True
        else:
            v.select = False
bmesh.update_edit_mesh(object, True)